The Field Controls CAS-34U Universal Combustion Air System is a mechanical air supply unit designed to provide controlled combustion air for fuel-burning HVAC equipment. It operates by delivering outside air into confined spaces in response to burner demand, ensuring proper combustion and safe operation. Commonly used with furnaces, boilers, and water heaters, this system enhances efficiency and supports compliance with building codes. Its application improves indoor air quality, reduces backdraft risks, and promotes consistent equipment performance while helping extend the lifespan of heating systems.